A situation where someone requires help but is not receiving it is unjust, because people's needs are not being met while others have more than they need. It is also unfair, because if you require help and have several randomly distributed attributes, you will receive that help, whereas if you require help and do not have those random accidents of birth you generally will not receive that help. That is definitionally unfair, because random chance is deciding the outcomes of people's lives.
This doesn't really makes sense. Two things that you mention, like determining what people need and role of random chance, don't have anything to do with justice.
For me, justice is fulfilment of obligations between people, that we either take explicitly (as promises or contracts), or a very limited number that should be implicitly upheld by all — about aggression and property. But while helping others is a good deed, I don't think anybody thinks you have an obligation to anybody except your own conciseness or g-d, if you believe in one.
And about random chance — that's your relationship with nature or g-d (again, used here not out of religious sense, but just a very useful rhetoric device), and they're not subjects to justice, because they're not people. Surely, you don't expect other people to have an obligation to correct nature or g-d's perceived mistakes or injustices?
I'm not the person you're talking to but I am autistic and I do experience a powerful obligation to help others in need. I feel it deeply in my very soul and I always have; I experience every choice not to act on it as a crushing moral and spiritual failure. I understand this isn't typical but surely you can see that it is a possible experience of the world for some people to have?
That does not contradict my point in any way. I do experience this "obligation" too, and help others, but I don't think this word fits here. But that's just an emotion — that's not a real obligation that I actually owe somebody except for myself.
Emotions are my own volition — I'm free to experience whatever I fee like. Real obligations are not; I have to respect them regardless of my internal emotional state.
It's the distinction between something that requires personal consent: my own decision to be charitable — and something that doesn't: my obligations. If I owe you money, you can use force to get it. You can't use force me to be charitable.
